Momentum Dependent Charge Excitations of Two-Leg Ladder: Resonant Inelastic X-ray Scattering of (La,Sr,Ca)14Cu24O41

TL;DR

This study uses resonant inelastic x-ray scattering to explore momentum-dependent charge excitations in a two-leg ladder compound, revealing unique doping behaviors and supporting a Hubbard model explanation.

Contribution

It provides new insights into charge excitations in ladder systems and demonstrates the formation of hole pairs through experimental and theoretical analysis.

Findings

Mott gap excitation shows little change with hole doping

Intraband excitation appears as a continuum at all momenta

Intraband intensity scales with hole concentration

Abstract

Momentum dependent charge excitations of a two-leg ladder are investigated by resonant inelastic x-ray scattering of (La,Sr,Ca)14Cu24O41. In contrast to the case of a square lattice, momentum dependence of the Mott gap excitation of the ladder exhibits little change upon hole-doping, indicating the formation of hole pairs. Theoretical calculation based on a Hubbard model qualitatively explains this feature. In addition, experimental data shows intraband excitation as continuum intensity below the Mott gap and it appears at all the momentum transfers simultaneously. The intensity of the intraband excitation is proportional to the hole concentration of the ladder, which is consistent with optical conductivity measurements.